1kg sour red or purple plums
1kg Chelsea Jam Setting Sugar

Wash plums and remove any stalks. Slice each plum into roughly 8 pieces, discarding the stones. Place in a large bowl or food processor and mash or process until coarsely crushed.

Combine with Chelsea Jam Setting Sugar in a large, heavy based pot. Stir over medium heat for a couple of minutes or until sugar dissolves.

Increase heat and bring to a full boil (a boil that cannot be stirred down). Boil rapidly for 4 minutes (removing any foam with a spoon).

Test a small amount of jam on a cold saucer (the surface should wrinkle when a spoon is pushed through it). If the surface doesn't wrinkle, return to the boil for 1-2 minute intervals and test again.

Ladle hot jam into warm sterilised jars and seal with a lid.

Set aside to cool, then label, date and store in a cool dark place. Refrigerate after opening.  Makes approximately 4 cups.